Note 6 - Leases (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2019	Jan. 01, 2019
Operating Lease, Weighted Average Remaining Lease Term	2 years 90 days	2 years 150 days
Operating Lease, Weighted Average Discount Rate, Percent	2.10%	2.10%
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 0
Operating Lease, Payments	150,000
Other Operating Income (Expense) [Member]
Operating Lease, Cost	374,000
Short-term Lease, Cost	$ 224,000
Minimum [Member]
Lessee, Operating Lease, Renewal Term	1 year
Maximum [Member]
Lessee, Operating Lease, Renewal Term	3 years